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Discussion Starter · #1 ·
Anyone out there have problems with GDP’s tuning on a 17 Titan XD Pro4x? Just hit 108k miles. I’ve installed the EZ lynk programmer no SOFT and have some weird issues. Set up: EGR intact, DPF removed. first issue: loaded 120hp v1.8 profile and truck ran fine day 1 no WOT. Day 2 drove truck 15 minutes still no WOT, shut down, started truck remotely then heard the engine lope like it was losing fuel pressure. Immediately cut the truck off, restarted with ignition, truck loped then shut off on its own. Primed fuel system, started and was able to get home. DTC showed U1300, U1266. Cleared fault installed 0hp v2.2, boost appears to be scavenging low pressure and high pressure turbos around 75mph, no fuel pressure issues. I have zero help from GDP as they state they have 1000s of trucks with these profiles and no issues. Reinstalled DPF system, returned to stock profile and boost seems normal, no fuel pressure issues. Flashed 0hp tune DPF/EGR installed/disconnected same boost failure but no fuel pressure issues (decided to rule out fueling). All tunes minus returning to stock appears to be scavenging for boost between low/high pressure turbos around 75mph. If I WOT the truck with any tune other than stock it pops a coolant flow restricted DTC P00B7 and puts the truck in limp mode (engine power reduced).
 

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The truth is, they don’t care about our trucks and no one actively wants to build a tune that is proper for our engines.

I can’t actually see what other tunes have done as no one openly shares them but if you have lots of turbine noise and the engine is holding boost at idle… the turbos are setup very badly.
 

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Discussion Starter · #3 ·
The truth is, they don’t care about our trucks and no one actively wants to build a tune that is proper for our engines.

I can’t actually see what other tunes have done as no one openly shares them but if you have lots of turbine noise and the engine is holding boost at idle… the turbos are setup very badly.
I agree. No one truly documents longevity enough to make a difference. The support from GDP was atrocious. First they said they don’t control turbine boost within the tunes, they only supply fuel demand. It sounds very stupid because an increase or decrease of fuel demand would have to correlate to turbine timing. It would be the equivalent of saying the tuning profile won’t change how your truck operates even if the turbo was missing. They told me “we sell 1000s of tunes for this vehicle without any issues, there’s something wrong with your truck.” I don’t care if 1000s of Titans run these tunes, if a customer is reporting an issue it should be treated as such and investigated. Instead, they basically told me they aren’t rewriting any tunes and don’t plan to change the current profiles. All I asked was for the issue I’m experiencing to be documented and investigated. I’ve lost faith in a company’s ability to actually assist a customer or troubleshoot a persistent failure. I’m not the type of engineer to shotgun parts at something hoping the problem goes away.
 

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I’m working on writing my own tune. It’s a long road but right now life’s obligations are in the way.

I can tell you this much: The ecm has complete and absolute control over fuel, boost, timing… everything.

It compares multiple tables, passes every decision through a number of managers that all then decide what to do. There is over 17,000 parameters on the calibration the tuned trucks are running.

If it sees something it doesn’t like, it defaults to whatever meets the bogus emissions standards it can achieve.

Commanding the bypass valve to stay open and only close to build boost has completely changed the sound of the truck. Telling it to hold 0psig of boost at 1800rpm during light throttle has made a massive improvement in fuel economy.

However, there are some serious problems with my tune. Because I command an open rotary valve, any time I tip in, it dumps a bunch of fuel and clamps down the rotary valve. I cannot stab the throttle unless I’m already in boost. It is a soot monster right now. Not rolling coal, but cold combustion.

The other major issues that are not obvious. For every change I’ve made, a number of emissions treatment and combustions managers are throwing red flags at what they’re seeing. turbine gain has been effected, timing, fueling, throttle response. All things that are not obvious and not shine in your face on the dash or throw a code you can easily pull.

The thing is, as diesel tuning rapidly grew, a bunch of idiots rolled coal and made the goverments appease the mouth breathers. During that time, tuners were working on engines they knew would only last hundreds of hours. Maybe thousands. Most guys turn up the power… if anything goes wrong, well it must have been the extra hp! Not the bad tune, never a bad tune!

I naively removed all the post injections… why would you need fuel after the main combustion event? It’s all for emissions right? The last post is, but the first post helps stabilize the piston in the cylinder and inject the remaining fuel that didn’t make it through the main shot.

So you have guys downloading bins directly from the ecm or converting a calibration to a bin, then using experience to figure out what table is what. Sometimes the configuration files get leaked. The configuration file for the xd didn’t get leaked until 2020. After production of the xd cummins was stopped. Who is going to properly update a tune for an engine that isn’t made anymore and there isn’t many of them on the road? As best I can tell, the bin everyone is using is from 2017 and the ecm editor they’re using has about 1000 of those 17000 parameters.
 

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Anyone out there have problems with GDP’s tuning on a 17 Titan XD Pro4x? Just hit 108k miles. I’ve installed the EZ lynk programmer no SOFT and have some weird issues. Set up: EGR intact, DPF removed. first issue: loaded 120hp v1.8 profile and truck ran fine day 1 no WOT. Day 2 drove truck 15 minutes still no WOT, shut down, started truck remotely then heard the engine lope like it was losing fuel pressure. Immediately cut the truck off, restarted with ignition, truck loped then shut off on its own. Primed fuel system, started and was able to get home. DTC showed U1300, U1266. Cleared fault installed 0hp v2.2, boost appears to be scavenging low pressure and high pressure turbos around 75mph, no fuel pressure issues. I have zero help from GDP as they state they have 1000s of trucks with these profiles and no issues. Reinstalled DPF system, returned to stock profile and boost seems normal, no fuel pressure issues. Flashed 0hp tune DPF/EGR installed/disconnected same boost failure but no fuel pressure issues (decided to rule out fueling). All tunes minus returning to stock appears to be scavenging for boost between low/high pressure turbos around 75mph. If I WOT the truck with any tune other than stock it pops a coolant flow restricted DTC P00B7 and puts the truck in limp mode (engine power reduced).
You aren’t getting any support from GDP because they didn’t write their tunes. They purchased their tunes (or were just a third party) for another company. The original company dissolved and became a new company, leaving those tunes for our trucks out of reach for GDP.

It’s convoluted, but my tuner was spilling the beans about that situation when he was revising a tune for me over the phone.
 

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Discussion Starter · #6 ·
You aren’t getting any support from GDP because they didn’t write their tunes. They purchased their tunes (or were just a third party) for another company. The original company dissolved and became a new company, leaving those tunes for our trucks out of reach for GDP.

It’s convoluted, but my tuner was spilling the beans about that situation when he was revising a tune for me over the phone.
After my week long back and forth phone call with GDP I would second guess anything you stated. I wouldn’t recommend anyone purchasing tunes from them. This is my daily driver and it’s stuck in limp mode now. I’m at a loss other than returning it completely stock and eating the cost of the programmer and tuning profiles. I don’t know of any other tuning for this specific truck.
 

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Discussion Starter · #7 ·
After my week long back and forth phone call with GDP I would second guess anything you stated. I wouldn’t recommend anyone purchasing tunes from them. This is my daily driver and it’s stuck in limp mode now. I’m at a loss other than returning it completely stock and eating the cost of the programmer and tuning profiles. I don’t know of any other tuning for this specific truck.
** Wouldn’t second guess **
 

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Discussion Starter · #11 ·
How did you get fuel injection demand? Ez lynk confuses the hell out of me… but I need to know demanded fuel for my own truck…
it was a tile option on the programmer via dashboard. If you click the tile it will give you the option to change it. It’s mapped as injection pressure (A) the desired injection pressure is labeled (D). I’m trying to understand the correlation in actual and delta. They seem pretty linear so far and the couyuns at GDP state (A) is actual (D) is desired. I need to do more research.
 

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it was a tile option on the programmer via dashboard. If you click the tile it will give you the option to change it. It’s mapped as injection pressure (A) the desired injection pressure is labeled (D). I’m trying to understand the correlation in actual and delta. They seem pretty linear so far and the couyuns at GDP state (A) is actual (D) is desired. I need to do more research.
The one I was primarily concerned with is exhaust back pressure. However my research suggests that due to the fact the isv has tuned length runners and siamesed intake ports the engine might be more efficient at higher rpm with less boost while pulling weight. I've got to get mine calculating combustion properly first obviously, but it's something I want to explore.

If I understand correctly: 1400rpm @ 10psig requests more fuel than 2200 rpm @ 2psig of boost.
 

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Discussion Starter · #13 ·
The one I was primarily concerned with is exhaust back pressure. However my research suggests that due to the fact the isv has tuned length runners and siamesed intake ports the engine might be more efficient at higher rpm with less boost while pulling weight. I've got to get mine calculating combustion properly first obviously, but it's something I want to explore.

If I understand correctly: 1400rpm @ 10psig requests more fuel than 2200 rpm @ 2psig of boost.
With it being a diesel exhaust back pressure is irrelevant.. all (most) pressure is used at the turbine. Diesels, jet/turbo shaft engines, etc have no need for back pressure at the exhaust.
 

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With it being a diesel exhaust back pressure is irrelevant.. all (most) pressure is used at the turbine. Diesels, jet/turbo shaft engines, etc have no need for back pressure at the exhaust.
Exhaust back pressure is measured before the turbos, also known as drive pressure. The lack of back pressure from the dpf on deleted trucks has a noticeable effect on the rotary valve response. In some conditions leads to aggressive hunting, or porpoising.
 

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Discussion Starter · #15 ·
Exhaust back pressure is measured before the turbos, also known as drive pressure. The lack of back pressure from the dpf on deleted trucks has a noticeable effect on the rotary valve response. In some conditions leads to aggressive hunting, or porpoising.
How does that correlate when DPF is removed and straight pipe or hood stacked exhausts are installed? Boost pressure shouldn’t change at that point since the energy applied at is used at the turbo right? The amount of energy not used (fuel) is emitted out the exhaust… trying to understand because this would mean most straight piped truck would have major boost leaks. From my knowledge of turbine motors on aircraft mainly turboshafts, I’ve never encountered back pressure being something changed NPT (power turbine speed).
 

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Discussion Starter · #16 ·
How does that correlate when DPF is removed and straight pipe or hood stacked exhausts are installed? Boost pressure shouldn’t change at that point since the energy applied at is used at the turbo right? The amount of energy not used (fuel) is emitted out the exhaust… trying to understand because this would mean most straight piped truck would have major boost leaks. From my knowledge of turbine motors on aircraft mainly turboshafts, I’ve never encountered back pressure being something changed NPT (power turbine speed).
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How does that correlate when DPF is removed and straight pipe or hood stacked exhausts are installed? Boost pressure shouldn’t change at that point since the energy applied at is used at the turbo right? The amount of energy not used (fuel) is emitted out the exhaust… trying to understand because this would mean most straight piped truck would have major boost leaks. From my knowledge of turbine motors on aircraft mainly turboshafts, I’ve never encountered back pressure being something changed NPT (power turbine speed).
After turbine speed is achieved, it should hit the compressor. All this should be occurring well prior to any exhaust or DPF piping if I’m thinking correctly. I’m pretty sure exhaust back pressure should be irrelevant… but I’ve been wrong before lol
 

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Perhaps we're not on the same page, so hopefully this don't come off as condescending or too elementary.

Turbochargers are spun by the heated mass of the combustion processes. In an ideal world a turbocharger has a drive pressure ratio of approximately 1:1. So if the turbo is making 10psig at the compressor outlet, there should be 10psig at the turbine inlet.

Our trucks use egr so they're designed to run with a higher than 1:1 pressure ratio. My observations have been that it tends to stick around 2:1 and the worst I recorded was ~6:1. At 6:1 that means there is 60psig of drive pressure to achieve 10psig of pressure at the compressor outlet. Obviously we're ignoring the nuances of density ratio, fuel, combustion temperature, etc, etc. The ecms also tend to favour a higher drive pressure ratio because it decreases the response time of the turbo.

On an emissions compliant engine some of the mass airflow going into the intake of the engine comes from the exhaust. So a higher than 1:1 drive pressure is required to ensure that exhaust goes into the intake. I imagine that's why it seems to hold around 2:1 at a bare minimum. When the ecm calls for 30psig of manifold pressure, the combustion manager considers and calculates how much of that will be egr. That is mass airflow the turbo does not directly have to provide, or alternatively, energy that is not passed through the turbine. The plumbing from the turbine output to the dpf acts like a large accumulator due to the pressure drop across the emissions components. That remaining pressure acts as a cushion, slowing down the velocity of the exhaust gas, giving the ecm more time to respond to changes in conditions.

On a deleted truck, there is no egr, but the ecm is still requesting the same boost levels, or more, depending on the tune. As best I understand it, up to 30% of the intake flow is made up of egr. That means the ecm will happily close down the rotary valve further to force the turbo to achieve that requested manifold pressure. When the ecm adjusts the rotary valve to compensate for environmental conditions, that curve is still mostly stock, so it causes the value to open and close too quickly causing the boost and exhaust pressure to spike. The reduced backpressure from the dpf can cause odd spikes in boost. I don't know the exact cause and I'm still guessing, but I believe that the drive pressure is allowed to escape too quickly, the charge air manager, clamps down the rotary valve, pressure spikes, boost spikes, then charge air opens the rotary valve until the manifold pressure stabilizes to the amount requested in the table. In my other thread about writing the tune I have a couple screen shots of what that looks like, but basically it's boost spiking up and the drive pressure spiking to get that boost in the first place. I had some measure of success playing with the turbocharger gain, but once I realized I need to address all the emissions stuff first, I stopped playing with that aspect of it.
 

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Discussion Starter · #18 ·
Perhaps we're not on the same page, so hopefully this don't come off as condescending or too elementary.

Turbochargers are spun by the heated mass of the combustion processes. In an ideal world a turbocharger has a drive pressure ratio of approximately 1:1. So if the turbo is making 10psig at the compressor outlet, there should be 10psig at the turbine inlet.

Our trucks use egr so they're designed to run with a higher than 1:1 pressure ratio. My observations have been that it tends to stick around 2:1 and the worst I recorded was ~6:1. At 6:1 that means there is 60psig of drive pressure to achieve 10psig of pressure at the compressor outlet. Obviously we're ignoring the nuances of density ratio, fuel, combustion temperature, etc, etc. The ecms also tend to favour a higher drive pressure ratio because it decreases the response time of the turbo.

On an emissions compliant engine some of the mass airflow going into the intake of the engine comes from the exhaust. So a higher than 1:1 drive pressure is required to ensure that exhaust goes into the intake. I imagine that's why it seems to hold around 2:1 at a bare minimum. When the ecm calls for 30psig of manifold pressure, the combustion manager considers and calculates how much of that will be egr. That is mass airflow the turbo does not directly have to provide, or alternatively, energy that is not passed through the turbine. The plumbing from the turbine output to the dpf acts like a large accumulator due to the pressure drop across the emissions components. That remaining pressure acts as a cushion, slowing down the velocity of the exhaust gas, giving the ecm more time to respond to changes in conditions.

On a deleted truck, there is no egr, but the ecm is still requesting the same boost levels, or more, depending on the tune. As best I understand it, up to 30% of the intake flow is made up of egr. That means the ecm will happily close down the rotary valve further to force the turbo to achieve that requested manifold pressure. When the ecm adjusts the rotary valve to compensate for environmental conditions, that curve is still mostly stock, so it causes the value to open and close too quickly causing the boost and exhaust pressure to spike. The reduced backpressure from the dpf can cause odd spikes in boost. I don't know the exact cause and I'm still guessing, but I believe that the drive pressure is allowed to escape too quickly, the charge air manager, clamps down the rotary valve, pressure spikes, boost spikes, then charge air opens the rotary valve until the manifold pressure stabilizes to the amount requested in the table. In my other thread about writing the tune I have a couple screen shots of what that looks like, but basically it's boost spiking up and the drive pressure spiking to get that boost in the first place. I had some measure of success playing with the turbocharger gain, but once I realized I need to address all the emissions stuff first, I stopped playing with that aspect of it.
Perhaps we're not on the same page, so hopefully this don't come off as condescending or too elementary.

Turbochargers are spun by the heated mass of the combustion processes. In an ideal world a turbocharger has a drive pressure ratio of approximately 1:1. So if the turbo is making 10psig at the compressor outlet, there should be 10psig at the turbine inlet.

Our trucks use egr so they're designed to run with a higher than 1:1 pressure ratio. My observations have been that it tends to stick around 2:1 and the worst I recorded was ~6:1. At 6:1 that means there is 60psig of drive pressure to achieve 10psig of pressure at the compressor outlet. Obviously we're ignoring the nuances of density ratio, fuel, combustion temperature, etc, etc. The ecms also tend to favour a higher drive pressure ratio because it decreases the response time of the turbo.

On an emissions compliant engine some of the mass airflow going into the intake of the engine comes from the exhaust. So a higher than 1:1 drive pressure is required to ensure that exhaust goes into the intake. I imagine that's why it seems to hold around 2:1 at a bare minimum. When the ecm calls for 30psig of manifold pressure, the combustion manager considers and calculates how much of that will be egr. That is mass airflow the turbo does not directly have to provide, or alternatively, energy that is not passed through the turbine. The plumbing from the turbine output to the dpf acts like a large accumulator due to the pressure drop across the emissions components. That remaining pressure acts as a cushion, slowing down the velocity of the exhaust gas, giving the ecm more time to respond to changes in conditions.

On a deleted truck, there is no egr, but the ecm is still requesting the same boost levels, or more, depending on the tune. As best I understand it, up to 30% of the intake flow is made up of egr. That means the ecm will happily close down the rotary valve further to force the turbo to achieve that requested manifold pressure. When the ecm adjusts the rotary valve to compensate for environmental conditions, that curve is still mostly stock, so it causes the value to open and close too quickly causing the boost and exhaust pressure to spike. The reduced backpressure from the dpf can cause odd spikes in boost. I don't know the exact cause and I'm still guessing, but I believe that the drive pressure is allowed to escape too quickly, the charge air manager, clamps down the rotary valve, pressure spikes, boost spikes, then charge air opens the rotary valve until the manifold pressure stabilizes to the amount requested in the table. In my other thread about writing the tune I have a couple screen shots of what that looks like, but basically it's boost spiking up and the drive pressure spiking to get that boost in the first place. I had some measure of success playing with the turbocharger gain, but once I realized I need to address all the emissions stuff first, I stopped playing with that aspect of it.
No need to apologize for explanations bud. I’m trying to understand the functions as well. I’m glad you have actual data points and are researching functionality of this engine. Not a lot of ppl do research or even test functions of their vehicles. I’m all about learning what I can. Let me know if I’m off topic with what you’ve explained.. but it sounds a lot like functions of the CBV (compressor bypass valve). I think it’s operation is linear to the RTC valve. Both of these valves act as a turbo wastegate. If the vehicle is in regen the CBV is completely closed and the RTC is rotated to increase the high pressure turbine’s speed. Now I’m not totally sure how back pressure metering comes into play with any of this in an applied factor. And what you’ve explained and documented sounds like something written into the ECM’s code probably for emissions function. But hardware is hardware and from my minor knowledge in turbo operations, back pressure should not be a factor for lag or turbine speed because it’s used at the compressor section. Now as far as the EGR, lots if not all modern internal combustion motors use this applied engineering. Even at the aircraft level. On this specific turbo set up the CBV’s function is to direct exhaust gases to their respective channels. In the event of EG regen this may be where your 2:1 or excessive pressure drop resides. It could be something in the sw that is hindering RTC to fully open the CBV (closing off EGR channels) when engine loading exceeds the ECMs capability to meter the barometric pressure and psi on demand.
 

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I thought we were talking about the turbine side. The CBV closes when all of the mass airflow is being produced by the low pressure turbo. The turbo charger setup on the isv is basically series-sequential. Functions as compound turbochargers until about 2200 rpm, then the cbv will close and all the mass airflow comes from the low pressure turbo. The high pressure turbo is so small, the tech at Nissan didn’t realize he had removed it, I had to point it out.
 

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Discussion Starter · #20 ·
Right…If the RTC is commanded to 1 of the 3 modes of operation and vacuum pressure is achieved by the CBV this would redirect energy to the EGR system or bypass valve. That could be where loss would occur. All this would be before the down pipe. In most sequential set ups, boost is primarily at the low pressure turbo. The small high pressure turbo is used to assist low end speed and bigger turbo’s lag due to energy applied (drive pressure). That’s why I’m bringing up the CBV, it’s not a variable operation. It’s open or closed. This would be considered watergate operation. I think the differential pressure calculated at the ECM isn’t exhaust back pressure. It’s the DPFs differential pressure sensor you are seeing. It’s used to determine soot load. I’ve attached the Cummins operations manual for reference in what you were describing.
 

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